1. Cross-Reference to Related Applications
Reference is hereby made to commonly-assigned copending U.S. patent application Ser. No. 774,716 entitled PHOTOGRAPHIC FILM UNIT AND CARTRIDGE ASSEMBLY filed in the name of Donald M. Harvey on Mar. 7, 1977.
2. Field of the Invention
The present invention relates to film cartridge assemblies for use with cameras and, more specifically, to a film cartridge assembly including a film disk rotatably mounted in a casing.
3. Description of the Prior Art
It has become commonplace in recent years to enclose photographic film in a cartridge, cassette, magazine or the like, designed to afford convenient loading of a camera. While, more typically, such enclosures have been configured to accommodate an elongated strip of photosensitive roll film, it is also known to provide a plurality of exposure areas in a generally circular array on a disk-shaped sheet of film and to rotate such sheet incrementally to bring successive exposure areas into alignment with the camera's optical axis for exposure. Typical advantages of such a film disk over roll film include the relative compactness of the film package and the relative flatness exhibited by the film.
An illustrative example of film disk arrangements includes that shown in U.S. patent application Ser. No. 774,716 entitled PHOTOGRAPHIC FILM UNIT AND CARTRIDGE ASSEMBLY filed on Mar. 4, 1977, in the name of Donald M. Harvey. A film disk is mounted on a central, toothed core to form a film unit adapted to be rotatably supported within a protective casing for insertion into a camera. The film disk has a plurality of image areas residing along a generally circular exposure region extending substantially around the core so that the disk may be rotated to bring individual image areas into alignment with an exposure window in the casing.
In the aforementioned patent application, the film unit includes a cover member having an opaque leaf portion which is rotatable with the film disk and core. When the cartridge is not in a camera, the leaf portion underlies the casing's exposure window to prevent light which enters through the window from fogging the film. The camera's film indexing mechanism engages the core teeth to rotate the film unit to sequentially index each image area into alignment with the exposure window. After the film disk has been rotated 360.degree., the cover member's leaf portion is again below the exposure window and the cartridge assembly can be removed from the camera.
While the cartridge assembly described in the Harvey application provides highly accurate indexing of the film unit, once the cartridge assembly has been placed in a camera and the film unit indexed to the first frame, the cartridge assembly cannot be removed from and then reinserted into the camera to expose the remaining frames without light fogging several frames, unless the operation is conducted under "dark" conditions. A cartridge assembly according to the present invention can be removed from a camera without risk of fogging any film frames.
Since the cover member of the Harvey application is rotationally fixed to the film disk, its leaf portion always covers one region of the disk, which region is, therefore, not available for exposure. A cover member which is rotatable independently of the film unit as in the present invention makes the entire film disk available to receive latent images.
The cartridge assembly of the Harvey application has provision for preventing inadvertent reuse of an exposed cartridge assembly. However, because the film unit's angular position after complete exposure is identical to its position before exposure, a complex locking system is required. In contrast, the present invention provides for less than 360.degree. of rotation of the film disk between the time the cartridge assembly is loaded into a camera and when it is removed therefrom. Accordingly, a less complex mechanism may be provided for a final locking function.